If you use the correct method to beat and folding the egg whites in the batter,the cake won't sink.If you mess up the beating and folding,no matter you invert the cake or not it will sink eventually.No,I did invert the cake right after removing from the oven but if i use the tubepan,I will invert a sponge the cake.:)If you want to take the cake out from the pan make sure it is completely cool and tab every side of the pan.Never use non stick baking pan.!!